Preparing for extreme cold when you’re

I booked to go to Tromso with friends and nearer the time I realised I don’t own any jumpers, coats or other warm clothing that would be suitable for the trip because I run warm like many autistics and don’t notice cold temperatures at all.
I wrote to Mountain Warehouse and asked if they could help me figure out what to do so I would survive without overheating or hyperthermia. They kindly sent me some gear to use!